package com.leech.rpc.server;

import io.netty.util.internal.ThreadLocalRandom;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event;
import org.apache.zookeeper.ZooKeeper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.leech.rpc.util.Constant;

public class ServiceDiscovery {
	 private static final Logger LOGGER = LoggerFactory.getLogger(ServiceDiscovery.class);
	 
	    private CountDownLatch latch = new CountDownLatch(1);
	 
	    private volatile List<String> dataList = new ArrayList<>();
	 
	    private String registryAddress;
	 
	    public ServiceDiscovery(String registryAddress) {
	        this.registryAddress = registryAddress;
	 
	        ZooKeeper zk = connectServer();
	        if (zk != null) {
	            watchNode(zk);
	        }
	    }
	 
	    public String discover() {
	        String data = null;
	        int size = dataList.size();
	        if (size > 0) {
	            if (size == 1) {
	                data = dataList.get(0);
	                LOGGER.debug("using only data: {}", data);
	            } else {
	                data = dataList.get(ThreadLocalRandom.current().nextInt(size));
	                LOGGER.debug("using random data: {}", data);
	            }
	        }
	        return data;
	    }
	 
	    private ZooKeeper connectServer() {
	        ZooKeeper zk = null;
	        try {
	            zk = new ZooKeeper(registryAddress, Constant.ZK_SESSION_TIMEOUT, new Watcher() {
	                @Override
	                public void process(WatchedEvent event) {
	                    if (event.getState() == Event.KeeperState.SyncConnected) {
	                        latch.countDown();
	                    }
	                }
	            });
	            latch.await();
	        } catch (IOException | InterruptedException e) {
	            LOGGER.error("", e);
	        }
	        return zk;
	    }
	 
	    private void watchNode(final ZooKeeper zk) {
	        try {
	            List<String> nodeList = zk.getChildren(Constant.ZK_REGISTRY_PATH, new Watcher() {
	                @Override
	                public void process(WatchedEvent event) {
	                    if (event.getType() == Event.EventType.NodeChildrenChanged) {
	                        watchNode(zk);
	                    }
	                }
	            });
	            List<String> dataList = new ArrayList<>();
	            for (String node : nodeList) {
	                byte[] bytes = zk.getData(Constant.ZK_REGISTRY_PATH + "/" + node, false, null);
	                dataList.add(new String(bytes));
	            }
	            LOGGER.debug("node data: {}", dataList);
	            this.dataList = dataList;
	        } catch (KeeperException | InterruptedException e) {
	            LOGGER.error("", e);
	        }
	    }
}
